The objective of the project is to study the biochemical mechanism(s) which lead to the formation of senile and diabetic cataract in human subjects. The roles of different enzymes, such as superoxide dismutase, glutathione peroxidase, catalase (both, catalatic and peroxidase activities), glutathione reductase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase in the defense of tissues against oxidative damage by superoxide anions, hydrogen peroxide, hydroxy radical and lipid peroxides will be studied. We have demonstrated the presence of GSH S-transferases along with other enzymes of the mercapturic acid pathway in the lens and have been able to deplete lens GSH with 1-chloro-2, 4-dinitrobenzene (CDNB). CDNB-treated lenses remain apparently clear up to 24 hours, but become more sensitive to oxidative damage. The role of various enzymes and reduced glutathione (GSH) in the maintenance of lens clarity and the mechanism of protein aggregation in GSH-depleted lenses subjected to oxidative stress will be studied. The CDNB-treated lenses transport out CDNB-GSH conjugate and oxidize 14C1 glucose to form 14C102 at a rate faster than the untreated lenses. The mechanism of transport of GSH-xenobiotics and the increased 14C02 formation from 14C1 glucose will be studied. The enzymes of the proposed sorbitol-6-phosphate pathway will be purified and their properties studied. The intermediary metabolites of this pathway, such as sorbitol, sorbitol-6-phosphate, sorbitol diphosphate, along with glucose, fructose, glucose-6-phosphate, fructose-6-phosphate, and fructose-1, 6-diphosphate will be determined in the normal and diabetic cataract lenses obtained from human and experimental animals. The aldose and aldehyde reductases will be purified from human tissues and their kinetic, structural, and immunological properties will be studied to understand the biochemical and genetic interrelationship. The effect of aldose reductase inhibitors on the activity of aldose and aldehyde reductases purified from various human tissues and on the glycolytic and auxiliary enzymes will be studied. The structural analysis of aldose and aldehyde reductases will help in developing specific aldose reductase inhibitors for the prevention of diabetic cataractogenesis.